1. Field of the Invention
The present invention relates to techniques for detecting the speed of an electric motor and particularly to techniques which utilize current zero crossing times of stator currents to determine motor speed.
2. Description of the Art
Many motor applications require motor controllers that can sense motor speed precisely. To sense motor speed, many controllers employ tachometers or other electromechanical devices to produce an electrical signal indicative of motor speed. In addition to being an additional initial motor cost, the accuracy of these devices can deteriorate over time thus requiring either periodic maintenance or eventual replacement.
Many present day motor controllers incorporate a microprocessor. Thus it would be desirable to use the computational ability of the microprocessor to determine motor speed, rather than adding an electromechanical speed detection device.